Radiographic imaging such as x-ray imaging has been used for a wide variety of applications in various fields. A typical x-ray imaging system includes an x-ray source generating x-ray beams to irradiate a region of interest (ROI), and an x-ray detector detecting the x-ray beams passing through the ROI. For applications such as radiotherapy, the ability to view a region of interest within a dense anatomy such as tumor as well as the body contour is necessary for exact treatment of the tumor while sparing healthy surrounding tissue. However, the dynamic range of signals of images can limit the ability to view both of these areas. One problem of prior art methods of using high x-ray intensity for imaging thick or dense tissue is that the body contour (such as the area near the skin surface) can be saturated in the images, and as a result, no useful information can be discerned.
Accordingly, there is a need for improving the design, construction and operation of radiographic systems to enhance the dynamic range of signals in the images produced by the systems. There is a need for an imaging method that can provide good image contrast over a wide range of body thickness for accurate diagnosis and positioning for treatment.